The present invention relates to rotating type machines including, but not limited to compressors, pumps, transmissions and engines, and particularly to lubricated radial or thrust bearings therein.
Rotating machines in general have mating axially or radially loaded surfaces such as those at a thrust bearing or radial bearing, respectively, in a compressor. These surfaces tend to be a location of high wear and usually require lubrication. Lubrication between the interfacing bearing surfaces is often facilitated by providing oil to recesses, a groove or clearance space (collectively, recesses) located between these surfaces for retaining oil. Another means of providing an oil retention space between interfacing bearing surfaces is to apply a phosphate coating to one or both of these surfaces, the coating forming micron-sized interstices in which oil is retained. Oil passed over the interfacing bearing surfaces creates a film of lubricant therebetween, which supports the bearing load and reduces the amount of friction, and thus the amount of wear, between the bearing surfaces. The provision of oil retention spaces between the bearing surfaces is intended to help facilitate the formation of this film.
Previous attempts at using recesses for retaining oil between the interfacing bearing surfaces have yielded unsatisfactory results. These recesses were formed having depths on the order of tens of thousands of an inch, and are believed to be too deep for providing a sufficient lubricant film between bearing surfaces. Lubricant captured in these recesses cannot be easily drawn out to lubricate the bearing and establish an oil film to hydrodynamically support the load. Conversely, if the recesses are too small or nonexistent an insufficient amount of lubricant may be received therein to establish the film or a film sufficient to support the bearing load and lubricate the bearing interface. Such a lack of lubricant allows the bearing load to overcome the hydrodynamic pressure provided by the inadequate film, and the oil is forced from between the interfacing bearing surfaces, allowing contact thereof.
Although the interstices formed in phosphate coatings may allow for adequate oil retention and establishment of the oil film between the bearing surfaces, these coatings do not adhere well to aluminum or powdered metal parts which are common bearing components in rotary machines. Further, during the process of applying the phosphate coating, it may undesirably interface with other parts, causing problems with the operation of the device.
A means for retaining oil between the interfacing bearing surfaces which is more effective than previously provided, and/or which avoids the problems mentioned hereinabove is desired.
The present invention provides a rotating type machine including a first moving member having a first surface and a second member having a second surface slidably interfacing with the first surface. The first and second surfaces have relative movement therebetween, and one of the first and second members is supported by the other member through the interface of their respective first and second surfaces. At least one of the first and second surfaces is provided with at least one recess therein. A liquid lubricant is provided between the first and second surfaces, and the lubricant is received in the recess. Relative to the surface in which the recess is provided, the recess has a typical depth of 0.002 inches but which may range between about 0.00125 and 0.0060 inches, and an area at the surface which ranges between about 1.767xc3x9710xe2x88x924 and 1.963xc3x9710xe2x88x923 square inches, whereby, during operation of the machine, a pressure spike is created in the lubricant above the recess, and first and second surfaces are hydrodynamically separated from each other by the pressure spike.
The present invention also provides a rotating machine including a rotating element, a sliding member having first and second surfaces, the rotating element engaging the sliding member and inducing a moment thereon, and a slotted member having third and fourth surfaces slidably interfacing with and moving relative to the first and second surfaces, respectively. At least one of the surfaces is provided with at least one recess therein, and liquid lubricant is provided between the interfacing surfaces, the lubricant being received in the recess. Relative to the surface in which the recess is provided, the recess has a maximum depth which ranges between about 0.00125 and 0.0060 inches, and a surface area which ranges between about 1.767xc3x9710xe2x88x924 and 1.963xc3x9710xe2x88x923 square inches, whereby, during operation of the machine, a pressure spike is created in the lubricant above the recess, the interfacing surfaces are hydrodynamically separated from each other by the pressure spike, and the moment is at least partially counteracted by the spike.
The present invention further provides a method of elastohydrodynamically separating a pair of slidably interfacing surfaces including: slidably interfacing a first member having a first surface and a second member having a second surface; relatively moving the first and second surfaces; collecting a quantity of lubricant in a recess located in one of the first and second surfaces; creating a pressure spike in the lubricant above the recess and between the first and second surfaces; and elastohydrodynamically separating the first and second surfaces with the pressure spike.
The rotating machine may be, but is not limited to, a compressor, pump, transmission or engine. The dimples or recesses may be, for example, spherically shaped, but other shapes (e.g., cylindrical, parallelepiped) may be employed provided that the depth of the recess and its area at the surface in which it is located are suitably selected in accordance with the present invention. The prescribed size and depth of the dimple produces, in the oil above the dimple, a pressure spike which supports the bearing load; the oil also lubricates the interfacing bearing surfaces.
In accordance with the present invention, the oil-receiving recesses or dimples may be incorporated into either thrust type bearings, radial type bearings, or planar sliding surfaces to reduce wear of the surfaces, thereby increasing the life of the parts and efficiency of the machine.